Is there any way to make a simple LAN port tester that can plug into an ethernet port and check for connectivity. I dont want to use the cable testers as it require both ends of a cable to be plugged in. I just want to test signal to a port.
A simple tester is nothing more than a Loopback jack. You tie the tx pairs to the rx pairs of a rj45 Ethernet jack and plug it into the network adapter. The link light should turn on, as well as the activity light. This is enough for the network equipment to negotiate a speed and connection, but would not be useful for data.
Pictured is one for gigabit. 10/100 only need half of this.
Personally, I've used this to turn on the leds of my android tv box, that only turn on with the Ethernet connection.